300kva tranny with 200A 208V secondary

[chris kennedy]

Customer wants to use an existing 300kva 480V primary to feed a new 208y/120 200A PNL.
How can I determine the min size OCPD and conductor size for the primary to handle inrush?
Is this even compliant?
Thanks

 

[Dennis Alwon]

I am not sure I understand why this would be an issue. Why is inrush a concern here?

 

[chris kennedy]

To get 200A out at 208V I could feed the primary with 100A at 480V. A 300kve tranny I would normally feed with 500MCM and a 400A OCPD.

Wondering if the 100A breaker would handle the inrush.

 

[under8ed]

I believe that since the transformer is much larger than required, you would like to provide it with as small as a feed as possible.There would be a problem with inrush if you only feed this with enough current to provide the 200 amps for the panel. I have used transformers larger than required, and have run up against inrush keeping them from powering up when feeding with less than about half of normal line current. This was using time delay fuses also, if using other protection, you may not even be able to go that low.
There are other issues with using such an over sized transformer, ours were temporary solutions opposed to a permanent installation.

 

[under8ed]

I was typing while you posted, but I do not believe that will be enough. You may with 200, but like I said, we were not using breakers.